Mirror support bracket

ABSTRACT

A mirror assembly for use in vehicles having a support bracket which provides an adjustment mechanism to position the mirror under a substantially constant clamping pressure over a wide range of ambient temperature conditions. The support bracket includes a generally spherical socket which receives a polymeric ball cup substantially enclosing a ball member extending from the mirror. A spring forces the cup and ball member into the socket and causes the polymeric cup to compress about the ball member. The bracket may be used on both header- and windshield-mounted mirror assemblies, and may include an adjustable clamping member forming a portion of the socket whereby the clamping pressure may be further adjusted.

FIELD OF THE INVENTION

This invention relates to mirror assemblies for use in vehicles, andmore particularly to mirror support brackets having an adjustable pivotwhich provides a substantially constant clamping pressure over a widerange of ambient temperature conditions.

BACKGROUND OF THE INVENTION

Vehicle interior rearview mirrors are commonly secured to either theheader area near the top of the windshield or directly to the insidesurface of the windshield in the forward vision area of the driver. Mosthave a ball member either extending from or into the mirror body toenable pivotal adjustment of the mirror. In one prior-known mirrorhaving a ball member extending out of the mirror, the ball is capturedin one end of a swaged tube. A helical compression spring is disposed inthe tube and engages a disk which, in turn, engages the ball member. Thedisk has a portion which partially conforms to the shape of the ball.Often a similar structure is duplicated at the opposite end of the tubeto connect the mirror to a mounting member. In addition, a cup membercan be substituted for the disk. Such structures are disclosed, forexample, in U.S. Pat. Nos. 3,367,616 to Bausch et al.; 3,635,435 toPerison, Sr.; 4,936,533 to Adams et al.; and 5,100,095 to Haan et al.Such "double ball" mirror support assemblies are typically fixed to theinterior surface of the windshield.

A substantial number of other rearview mirrors are header-mountedmirrors. Examples of such assemblies are disclosed in U.S. Pat. Nos.4,012,022 to Tomita; 4,066,235 to Hashiguchi; and 4,826,289 toVandenbrink et al. In substantially each instance, a ball memberextending from the mirror stay or support arm is received in a socketwithin the rearview mirror assembly itself, such socket being formedeither by the mirror housing or by a pair of cooperating spaced apartplates. In either case, threaded fasteners draw the socket or spacedplates together within the mirror assembly to exert pressure on the ballto hold the mirror in a desired position. These fasteners are typicallyinaccessible for adjustment.

In each of the mirror assemblies described above, the clamping pressureon the ball is fixed at the instant it is assembled. As temperatureincreases or decreases, the clamping pressure changes as a direct resultof the different coefficients of expansion and contraction of thematerials. On one day, the ball joint may be stiff and difficult toadjust; while on other days the mirror may be loose and not stay inplace.

Another disadvantage of the mirror assemblies described above is theinability to interchange mirror heads. When a ball pivot extends fromthe mirror mounting arm into the mirror housing, the housing must bespecifically designed to accept that ball member on a permanent basis.Changing support arms for specific mirror heads and vice-versa withoutpartial destruction of the mirror was impossible. Furthermore andrelated thereto is the inability to replace one of the components of themirror assembly if it breaks; consequently, the entire mirror assemblyis usually replaced. The desire to change mirror heads, stays, orreplacement parts results in a replacement of otherwise perfectly goodcomponents and increases cost to the consumer.

SUMMARY OF THE INVENTION

The present invention provides a rearview mirror support bracket forvehicles having an adjustable pivot capable of receiving one of a numberof rearview mirror heads and provides a substantially constant clampingpressure through a range of ambient temperature conditions.

Generally, the present invention includes a mirror stay or support arm,preferably having one end attached to the vehicle by a breakaway,detachable coupling which allows the stay to separate upon theapplication of a predetermined force. The opposite end of the supportarm includes a ball-mount retention assembly. The assembly includes asocket for receiving the ball mount extending from the mirror. The ballmount is substantially enclosed by a compressible cup which frictionallyengages the ball mount. A spring at one end of the cup and engaging themirror stay forces the cup in a direction on the socket which, in turn,forces the cup tighter about the ball mount.

In one embodiment, the bracket assembly includes a stay with a socketformed at one end by cooperating hinged portions. A cup disposed in thesocket also substantially encloses the ball extending from the mirror.The ball and cup are clamped in the socket by the cooperating hingedportions. A biasing member is disposed in the socket to force the cupand enclosed ball against one end of the socket to compress the cuptightly about the ball. The spring and cup together maintain asubstantially constant clamping pressure on the ball through awide-range of temperatures.

In a preferred embodiment of the invention, the socket is defined byopposing depressions: one in a fixed end of the mirror stay, and theother in a cap to engage the fixed end. The cap has a hole in one end toreceive a hook extending from the fixed end. A screw secures an oppositeend of the cap to the stay. The ball member extending from the mirror issubstantially enclosed by a polymeric cup which, in turn, is received inthe socket. The cup includes a plurality of movable segments which clampagainst the ball when compressed. A spring is disposed at one end of thecup opposite an opening accepting the ball, to force the cup against theopening and force the segments against the ball, thereby exerting asubstantially constant clamping force on the ball.

In an alternate embodiment of the invention, the stay has one endattached to the vehicle and the opposite end terminates in a dependenthousing having a generally oval peripheral edge. A recess is defined onan opposite or back side and is concealed by a cover. A hole extendsthrough the housing large enough to allow the ball mount to passtherethrough. A cup member disposed on the recess side of the housingsubstantially encloses the ball mount and prevents the ball from beingwithdrawn through the hole. The cup includes a plurality of segmentswhich compress about the ball mount when forced against the hole. Aspring at the back of the cup and anchored in the recess forces the cupagainst the hole and maintains a substantially constant clampingpressure on the ball mount.

Preferably, each embodiment of the bracket assembly also includes abreakaway mounting assembly, which allows the support bracket to releasefrom the vehicle header or other vehicle portion to which the bracket issecured upon sustaining a predetermined impact force such as during anaccident.

As will be understood, the present invention provides numerousadvantages over prior mirror support brackets. The mirror bracketassembly exerts a substantially constant clamping pressure on the ballextending from the mirror over a wide range of ambient temperatureconditions. The mirror bracket also accepts a wide array of mirror headtypes without replacing the bracket. The clamp assembly, internal cup,and spring can also adapt balls of different sizes to the bracket. Theclamp assembly can also be easily incorporated in conventional breakawayheader- or windshield-mounted mirror assemblies, which allow the supportand rearview mirror to release from the vehicle.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A better understanding of the invention and the advantages providedthereby may be obtained by reference to the specification and theattached drawing figures, wherein:

FIG. 1 is a fragmentary, perspective view of a header-mounted mirrorassembly incorporating one embodiment of the invention and installed ona vehicle;

FIG. 2 is a fragmentary, side elevational view of the mirror assemblyshown in FIG. 1;

FIG. 3 is a top view of the mirror assembly;

FIG. 4 is a fragmentary, exploded view of one embodiment of theinvention shown in FIGS. 1-3;

FIG. 5 is a fragmentary, side-section view of the embodiment of theinvention in FIG. 4;

FIG. 6 is a fragmentary, front-elevational view of the embodiment of theinvention in FIG. 4;

FIGS. 7-9 are side and front views of one embodiment of a cap used inthis invention;

FIGS. 10-13 are front, side, and sectional views, respectively, of oneembodiment of a cup used in this invention;

FIGS. 13 and 14 are front and sectional views of one embodiment of aspring used in this invention; and

FIGS. 15-17 are fragmentary sectional views of an alternate embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing figures, mirror assembly 20 is shown mounted toan interior header 22 of a vehicle close to the upper edge 24 ofwindshield 26. Assembly 20 is attached to header 22 by a securing member28 retained by screws 30 extending therethrough and extending into sheetmetal 32 concealed by headliner 34 (FIG. 2). Attached to securing member28 and dependent therefrom is a mirror stay or support arm 36 having afirst end 38 forming a base 40. Base 40 is preferably coupled tosecuring member 28 using a breakaway connection, such as described ingreater detail below. Another example of such a coupling is disclosed incommonly assigned U.S. Pat. No. 5,100,095 to Haan et al. The couplingbetween base 40 and securing member 28 allows separation of base 40 frommember 28 should an impact occur.

As an alternative to securing member 28 attached to header 22 as seen inFIG. 1, member 28 and base 40 may be attached to the interior surface ofwindshield 26 by a conventional mounting button adhered to thewindshield surface by a layer of conventionally known metal-to-glassadhesive such as a polyvinyl butyral available from Monsanto Company ofSt. Louis, Mo. Securing member 28 would then be designed to be slidablyreceived over the mounting button to suspend mirror assembly 20 fromwindshield 26.

An opposite end 42 of stay 36 terminates in a ball-mount retentionassembly 44. Assembly 44 receives a ball member 46 disposed at one endof an arm 48 extending from the back 50 of mirror 52 such as disclosedin commonly assigned U.S. Pat. Nos. 4,936,533 to Adams et al. and5,100,095 to Haan et al. Referring to FIG. 2, ball member 46 projectsfrom a day/night pivot actuator 54 rotatably mounted within rearviewmirror housing or frame 56 on upper pivot shaft 58. Frame 56 enclosesand retains a prismatic mirror element 60 having nonparallel front andrear surfaces. A pivot lever 62, supported on a lower pivot shaft 64 andjoined integrally to the lower edge of pivot actuator 54, may be movedback and forth to pivot frame 56 and prism 60 between day and nightreflective positions about shaft 58. In the day position, substantiallyall of the light incident upon the second, reflective coated, rearsurface of the prism from the rear of the vehicle is reflected to theeyes of the driver. In the night position, when the mirror case andprism are pivoted about shaft 58, a significantly reduced amount oflight is reflected from the non-reflective coated front surface of prism60, thereby reducing glare and improving the driver's night vision.

To reduce the weight of mirror assembly 20, lightweight yet rigidmaterials are used to make the various components. For example, it ispreferred that securing member 28, mirror frame 56, pivot actuator 54,and pivot lever 62 be formed from a polymeric material. Mirror stay 36is preferably die cast from S.A.E. zinc 925, although aluminum, or otherrelatively lightweight materials, could also be used. Further costsavings and structural benefits are obtained by a recess 66 extendingsubstantially the length of stay 36, extending inwardly from a sideclosest to windshield 26. Recess 66 substantially parallels thelongitudinal axis of stay 36 and defines lateral walls terminating inend walls proximate each end of stay 36. Lateral walls essentially actlike I-beams, providing the strength while reducing a substantial amountof material and weight from stay 36.

Referring now to FIGS. 4-6, one embodiment of retention assembly 44includes a fixed jaw portion 70 extending from end 42 and having alateral, flat surface 72 contained substantially in a plane includingthe longitudinal axis of stay 36. Surface 72 extends toward second end42 before terminating in a shoulder 74. Surface 72 includes a generallyhemispherical depression 76 formed by wall 78. Between shoulder 74 anddepression 76 is a threaded hole 80 which extends into surface 72 toreceive a threaded fastener described below. Located at the lower end ofsurface 72, below depression 78, is a hook, finger, or tenon 82 forreasons which will become apparent below.

Cooperating with fixed jaw 70 and engaging surface 72 is a cap 84generally constituting a mirror image of fixed jaw 70 from shoulder 74downward (FIGS. 7-9). Cap 84 is preferably die cast from S.A.E. 903 or925 zinc, although other materials may also be used. Cap 84 includes asurface 86 containing a generally hemispherical depression 88, whichwhen coupled to fixed jaw 70, defines a generally spherical cavity orsocket 90 shown in FIGS. 2 and 5. Below depression 88 is a hole ormortise 92 extending through wall 94 and separated from surface 86 by abridge 85 and adapted to receive hook or tenon 82 described above. Abovedepression 88 and extending through cap 84 is hole 96 aligned with hole80 in jaw 70. Hole 96 includes a recess 98 on the opposite side toreceive and recess the head 100 of threaded fastener 102 extendingtherethrough and received in threaded hole 80 (FIGS. 4, 6). Locatedbehind depression 88 and extending approximately 0.25 to 0.75 millimeter(mm) perpendicularly from surface 86, is boss 104, which provides auniform space between the rear edge 89 of cap 84 and the cooperatingedge on the fixed jaw 70. The exterior surfaces and profiles 87 of cap84 and fixed jaw 70 are generally identical, mirror images of each otherto form the generally spherical clamp assembly 44 and provide sufficientroom for socket 90.

Referring to FIGS. 4-6, socket 90 is accessible through an opening 106formed in front surface 108 of clamp 44 by cooperating edges 110, 112.Opening 106 is such to allow reasonable room for the vehicle operator toadjust mirror 52, yet retain ball member 46 therein, and with adimension less than the diameter of ball 46 to prevent ball member 56from escaping when assembled. The inner surface of socket 90 defined byinterior wall 114 is generally spherical and contains a pair ofcylindrical grooves 116, 118 formed therein and concentric with oneanother. Groove 116 is preferably contained in a plane substantiallyparallel to front surface 108 and located along the greatest diameter ofsocket 90. Groove or channel 118 is parallel to groove 116 and locatedbetween groove 116 and the bottom or back wall 120 (FIG. 9). Channels116, 118 in socket 90 receive and retain cup 122 and a disk-shapedspring 124, respectively, both described below.

Cup 122 (FIGS. 10-12) is preferably formed from a polymeric material,most preferably on acetal resin which is a hard, tough plastic oftenused as a substitute for many metals. A preferred acetal resin is CelconUV-90 available frown Hoechst-Celenese of Chatham, N.J. Cup 122 ispreferably molded having a substantially smooth spherical interior wall126 designed to closely conform to ball member 46 received thereinthrough opening 128 having generally the same dimension as does opening106. The exterior wall 130 is also generally spherical in form toconform to the interior 114 of socket 90. Extending from exterior wall130 is a circumferential flange 132 contained in a plane substantiallyparallel to opening 128. Flange 132 is dimensioned to be received insocket groove 116. In a preferred embodiment, cup 122 contains aplurality of slots 134, preferably four, extending from opening 128 to apoint slightly beyond flange 132. Slots 134 are preferably equidistantfrom each other and are contained in two imaginary planes intersectingeach other at a right angle. Slots 134 define an equal number of cupsegments 138 which are able to flex to increase and decrease theinterior diameter of wall 126 as well as the size of opening 128.

Spring 124 (FIGS. 13, 14) is a disk-like member preferably formed fromspring steel and most preferably S.A.E. 1050 annealed spring steel, heattreated by the process of austempering. The steel is most preferablyfinished with zinc plate and black di-chromate to prevent corrosion. Thespring is preferably circular in shape and of a dimension to fit withinchannel 118 in socket 90. A hole 140 is formed in the spring 124,passing through the center thereof, to receive a projection 142extending from a flat 144 (FIGS. 11, 12) at the back of cup 122 suchthat spring 124 lies adjacent flat 144. Spring 124 may also contain oneor more dimples 146 to aid in separating each disk after manufacturing.Although spring 124 is described as a circular disk, other spring shapesmay also be employed including rectangular, square, hexagonal,cross-shaped, leaf, or coiled springs.

Referring again to FIGS. 5, 6, ball member 46 is pressed into theinterior 126 of cup 122 by inserting ball 46 through opening 128,spreading cup segments 138 apart in doing so. Spring 124 is attached tothe back 144 of cup 122 by projection 142 extending through hole 140.Cup 122 and ball member 46 are placed in the disassembled socket 90 suchthat circumferential flange 132 is located in channel 116. Spring 124 isreceived in channel 118 such that the peripheral edge of the springengages shoulder 121 and the center of the spring is spaced from back120. Cap 84 is aligned with fixed jaw 70, with hole 92 receiving hook 82and aligned so that spring 124 and cup flange 132 are located in theirrespective channels. Screw 102 is inserted through hole 96 and threadedinto hole 80 in fixed jaw 70, and adjusted to clamp cup 122 and cupsegments 138 about ball member 46. Spring 124 disposed in the bottom ofsocket 90 forces cup 122 forward in socket 90 against lip 110 which, inturn, causes cup segments 138 to be further compressed about ball member46. The conformance of cup interior 126 to the exterior of ball member46, the adjustable clamping action of cap 84 with jaw 70, and spring 124acting on cup 122, combine to provide a frictional coupling which exertsa substantially constant clamping action on ball member 46 through awide range of ambient temperature.

The clamping force may be adjusted by screw 102 forcing the end ofclamping plate or cap 84 against the upper end of fixed jaw 70. Thefixed points established by hook 82 in hole 92, and boss 104 extendingfrom cap 84, cause socket 90 to close about the end having opening 106.The compression of socket 90 at the end containing opening 106 forcescup segments 138 tightly inward against ball member 46 to place morefriction on ball member 46 if necessary. Compression of cup 122 atopening 106 tends to move cup 122 back away from opening 106. However,spring 124 at the back of cup 122 reacts by forcing cup 122 towardopening 106. The result is a substantially constant clamping pressure onball member 46.

Referring to FIGS. 15-17, an alternate embodiment of mounting system 200for attaching a rearview mirror 202 to a vehicle header 204 includes amirror stay or support arm 206 having a first base end 208 detachablycoupled to a securing member 210 which, in turn, is fixed to the vehicleheader 204. Base 206 may be attached to securing member 210 in a numberof ways and is preferably coupled in a manner such that base 208 breaksaway or releases from securing member 210 upon a substantial forceexerted upon stay arm 206.

The opposite end 212 of stay arm 206 terminates in a ball-mountretention assembly 214. Assembly 214 receives and retains a ball member216 at an end of a ball arm 218 extending from the back of the rearviewmirror 202, such as disclosed in U.S. Pat. Nos. 4,936,533 and 5,100,095.Ball member 216 projects from a day/night actuator 54 rotatably mountedon shafts 58, 64 within the mirror housing or frame 56 as describedabove.

Ball-mount retention assembly 214 includes a housing 220 having agenerally flat front surface or face 222 with a generally oblong or ovalperipheral edge 224. Opposite face 222, on a back of assembly 214, is arecess 226 having an upper shoulder 228, a floor 230 generally parallelto face 222, and a lower flange 232. Formed in floor 230 and extendingthrough to face 222 is a spherical hole or socket 234 having a largerdiameter in floor 230 than in face 222. The diameter of socket 234 inface 222 is sufficiently large to pass ball member 216 therethrough.

Capturing and substantially surrounding ball member 216 in recess 226 isa ball cup 236 preferably formed from a polymeric material, and mostpreferably an acetal resin such as Celcon UV-90 described above. Cup 236has a substantially smooth spherical inner-wall 238 designed to conformclosely to ball member 216 received therein through opening 240. Theouter surface 239 of cup 236 adjacent cup opening 240 conforms closelyto the spherical surface defining socket 234. On cup 236 oppositeopening 240 is a projection 242 to be used to properly position andsustain the position of cup 236 in socket 234.

In the preferred embodiment, cup 236 includes a plurality of slots 241which extend from opening 240 partially back toward projection 242.Slots 241 are preferably spaced equidistant from each other to define alike number of cup segments 243. Each segment 243 is designed to expandand increase the size of opening 240 to allow ball member 216 into thespherical chamber formed by wall 238. Each segment is also designed tobe forced inwardly against ball member 216 by socket 234 when cup 236 ispushed from behind by spring 252. The compression of the segments aboutball member 216 increase the friction, and, as a result, retain rearviewmirror 52 in position.

Received about projection 242 and having a first end 244 engaging a slot246 in top wall 228 and an opposite end 248 received in a slot 250 inflange 232 is a spring 252, forcing cup 236 into socket 234. Spring 252is preferably generally rectangular in shape and made from S.A.E. 1050annealed spring steel, austempered to provide optimum behavioralcharacteristics. Spring 252 is most preferably finished with zincplating and black di-chromate to prevent corrosion. Formed at each end244, 248 are slots 254, 256 to allow a tool to bend and compress spring252 so as to engage the slots 246, 250 in recess 226.

Concealing recess 226 and fitting generally flush with peripheral edge224 and the exterior surface of stay 206 is a cover 258. It is preferredthat cover 258 be molded from a polymeric material such as PVC and havea shape, texture, and color that conforms and blends with that providedon stay 206. Cover 258 is intended to attach securely to the retentionassembly 214, yet be easily removed in order to remove spring 252 andallow the replacement of mirror 202, without the need to replace stay206.

Referring back to FIGS. 1-3, it is intended that any embodiment of theinvention be used in conjunction with what is known as a "break-away"mirror mounting assembly such as disclosed above, or in Japanesepublication 57-55239. As shown in the drawing figures, securing member28 includes a recess 150 for retaining a spring washer 152 havinginwardly projecting fingers 154. Extending through the center of washer152 is a bolt 156 with the head 158 engaging fingers 154. The threadedend of bolt 156 is received in stay base 40 to hold base againstsecuring member 28. The lower surface 160 of securing member 28 containsa plurality of recesses 162 to be engaged by a like number ofprojections 164 extending from base 40. When an impulsive force tendingto rotate stay 36 in a direction indicated by arrow 166 (FIG. 2), or ina direction indicated by arrow 168 (FIG. 3) where bolt 156 is the pivotpoint, bolt head 158 is drawn through the fingers 154 of spring washer152 and stay 36 separates therefrom, absorbing the forces causing theseparation.

The above description is considered that of the preferred embodimentsonly. Modification of the invention will occur to those skilled in theart and to those who make and use the invention. Therefore, it isunderstood that the embodiments shown in the drawings and describedabove are merely for illustrative purposes and are not intended to limitthe scope of the invention, which is defined by the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A single ball jointsupport bracket for a vehicle rearview mirror housing, the mirrorhousing having a ball member extending therefrom, comprising:a mirrorstay having a first end terminating in a single, generally spherical,ball joint socket; a cup, substantially enclosing the ball memberextending from the mirror housing, disposed within said generallyspherical ball joint socket, and having a rear surface; and a biasingmember disposed in said generally spherical, ball joint socket behindsaid cup, to force said cup toward one end of said socket and compressabout the ball to sustain a substantially constant clamping force on theball through a range of ambient temperatures, said biasing memberincluding at least one of a disk, rectangular, square, hexagonal, leaf,and coil spring.
 2. A support bracket for a vehicle rearview mirrorhousing, the mirror housing having a ball member extending therefrom,comprising:a mirror stay having a first end terminating in a generallyspherical socket, said socket being defined by a first portion from saidfirst end, and a second cooperating portion coupled to said firstportion; a cup substantially enclosing the ball member extending fromthe mirror housing, and disposed within said generally spherical socket;and a biasing member disposed in said generally spherical socket behindsaid cup, to force said cup toward one end of said socket and compressabout the ball to sustain a substantially constant clamping force on theball through a range of ambient temperatures.
 3. The mirror support asdefined in claim 2, wherein said cup is retained in said socket betweensaid first and second portions.
 4. The mirror support as defined inclaim 3, including an adjustable fastener for drawing said first portiontoward said second portion to tighten said cup about the ball member. 5.The mirror support as defined in claim 2, wherein said stay includes asecond end attached to a substrate.
 6. The mirror support as defined inclaim 5, wherein said substrate includes a vehicle.
 7. The mirrorsupport as defined in claim 6, wherein said substrate includes aheadliner.
 8. The mirror support as defined in claim 6, wherein saidsubstrate includes a windshield.
 9. The mirror support as defined inclaim 2, wherein said first portion includes a generally hemisphericaldepression having a convex outer surface and a corresponding concaveinner surface.
 10. The mirror support as defined in claim 9, whereinsaid second portion includes a generally hemispherical cap member havinga convex outer surface and a corresponding concave inner surface, andattached to said first portion to form said socket.
 11. A rearviewmirror assembly for a vehicle, comprising:a mirror housing having aback; a ball member extending from said back of said mirror housing; amirror stay having first and second ends, said first end attached to thevehicle, said second end defining a first portion of a generallyspherical clamp; a clamping member defining a second portion of saidgenerally spherical clamp detachably coupled to said first portion andcooperating with said first portion to define a socket; a ball cupdisposed about said ball member and received within said socket, saidcup having at least one segment compressible about said ball member bysaid clamp; and a biasing member disposed between said ball cup and saidsocket for urging at least one segment about said ball member.
 12. Themirror assembly as defined in claim 11, wherein said coupling of saidsecond portion of said generally spherical clamp to said first portionincludes a hinge assembly.
 13. The mirror assembly as defined in claim11, wherein said coupling of said second portion of said generallyspherical clamp is coupled to said first portion includes a threadedfastener.
 14. The mirror assembly as defined in claim 12, wherein saidhinge assembly includes:a hook member extending from at least one ofsaid first portion and said second portion of said generally sphericalclamp; and a slot defined in a remaining one of said first and secondportion of said generally spherical clamp to receive said hook member.15. The mirror assembly as defined in claim 14, further including anadjustable fastener at an end opposite said hook member and slot formoving said clamping plate against said first portion to increaseclamping pressure on said ball cup and ball member.
 16. The mirrorassembly as defined in claim 11, wherein said ball cup includes:a moldedpolymeric, generally spherical sleeve having an opening for receivingsaid ball member, said sleeve conforming closely to said ball member; atleast one slot formed in said sleeve and extending from said opening todefine at least one compressible cup segment; and a flange extendingfrom an exterior surface of said ball cup for positioning said ball cupin said socket.
 17. The mirror assembly as defined in claim 11, whereinsaid ball cup includes a member extending from an exterior surfacethereof for positioning said biasing member with respect thereto and insaid socket.
 18. The mirror assembly as defined in claim 17, whereinsaid biasing member includes a spring.
 19. The mirror assembly asdefined in claim 18, wherein said member extending from said ball cupexterior includes a flange; said socket formed by said clamping plateincluding at least one channel formed in an interior wall thereof toreceive said flange extending from said ball cup and a recess forreceiving said spring.
 20. A breakaway rearview mirror assembly for avehicle, comprising:a securing member attached to the vehicle; a supportarm having a first and second ends; a breakaway coupler extendingthrough said securing member for releasably coupling said first end ofsaid stay to said securing member and allowing said coupler to releaseand separate from said securing member upon impact by a force ofpredetermined magnitude acting on said stay; a ball-mount retentionassembly defined at said second end of said support arm and defining agenerally spherical cavity having an opening therein; a compressibleliner cup disposed within said spherical cavity; a spring disposedbetween said spherical cavity and said compressible liner cup oppositesaid opening; and a ball mount extending from a rearview mirror, saidball mount being received in said liner cup through said opening andclamped in place in said spherical cavity by said compressible liner cupand spring.
 21. The breakaway rearview mirror assembly as defined inclaim 20, wherein said ball-mount retention assembly includes:a fixedjaw defined on said second end of said stay and containing a depression;a moving jaw attached to said fixed jaw and containing a depression; andsaid spherical cavity defined by the cooperation of the depression ineach jaw.
 22. The breakaway rearview mirror assembly as defined in claim21, further including an adjustable fastener for drawing said moving jawtoward said fixed jaw to tighten said cavity about said liner cup. 23.The breakaway rearview mirror assembly as defined in claim 20, whereinsaid ball-mount retention assembly includes:a fixed portion dependentfrom said second end of said stay having a face on one side and a recesson a second and opposite side; a hole extending through said fixedportion and having a sphere conforming inner surface and having adimension to freely receive said ball mount therethrough; said liner cupdisposed on said recess and receiving said ball mount therein, saidliner cup having a generally spherical surface engaging said innersurface of said hole; and said spring disposed in said recess andengaging said liner cup for forcing said liner cup into said hole andclamping said liner cup about said ball mount.
 24. The breakawayrearview mirror assembly as defined in claim 23, further including acover received over said recess and concealing said spring and linercup.